Seal ring and joint

ABSTRACT

A seal ring (4) and connection joint (1) for connecting and sealing conduits/pressure vessels (2, 3) and the like is disclosed. The seal ring comprises a sealing portion (5) having a pair of seal lips (6, 7) sloping radially outwardly to a web portion (8), the web portion extending radially outwardly to a spigot (9) having portions projecting transversely to the web. The thickness of the spigot in the radial direction (w) is substantially greater than the thickness of the web in the transverse direction (t), and the seal lips project transversely from the web by a distance (h) which is substantially greater than the thickness of the web in the transverse direction (t). This configuration provides improved seal characteristics. The joint (1) comprises the seal ring interposed at the interface between two conduit (or vessel) members (2, 3), the conduit or vessel members being provided with respective recesses (10, 11) arranged to receive the sealing lips and spigot of the seal ring.

BACKGROUND OF THE INVENTION

The present invention relates to a seal ring and connection joint forconduits, pressure vessels or the like.

When connecting adjacent sections of fluid flow conduits or vessels,seal rings are typically interposed at the interface of adjacentconnecting ranged conduit or vessel portions which are then boltedtogether. Where high pressure or corrosive fluid is carried in theconduit or vessel, the seal ring used is typically metallic, the sealbeing effected by elastic or plastic deformation of a sealing surface ofthe seal ring against sealing portions of the ranged portions.

Known seal rings and joints of the general type are disclosed, forexample in U.K. patent specifications 742213, 854189, 952755, 1035958and 1521546, and PCT specification WO91/19128.

SUMMARY OF THE INVENTION

We have now devised an improved seal ring and associated connectionjoint.

According to a first aspect of the invention, there is provided anannular seal ring comprising an integrally formed sealing portion,spigot portion and interconnecting web portion, said sealing portioncomprising a pair of annular seal lips facing the spigot portion andextending in a transverse direction to said web portion, which webportion extends radially outwardly from said pair of seal lips to saidspigot portion, which spigot portion is provided with spigot projectionsprojecting in mutually opposed directions transversely to the webportion, wherein the thickness of said spigot portion in the radialdirection is substantially greater than the thickness of the web portionin the transverse direction, and each respective seal lip is arranged toproject transversely from said web portion by a distance which issubstantially greater than the thickness of said web portion in saidtransverse direction.

It is preferred that the thickness of the spigot portion in the radialdirection is substantially greater than the thickness of the web in thetransverse direction over substantially the whole transverse extent ofthe spigot portion.

The pair of annular seal lips are preferably arranged each on arespective radially outer portion of the sealing portion, andadvantageously slope radially outwardly and toward one another to theweb portion.

It is preferred that each spigot projection is provided with arespective first transverse face portion facing a respective seal lip,which transverse face portion is advantageously disposed substantiallyperpendicular to the radial direction.

Typically, each spigot projection is provided with a respective secondtransverse face portion spaced from the respective first transverse faceportion and facing in an opposed direction thereto. Advantageously, thefirst and second transverse face portions provided on each spigotprojection are substantially parallel to one another.

Typically, the second transverse faces comprise the radially outermostextent of the seal ring. Advantageously the second transverse faces arecoplanar thereby defining a substantially continuous annular radiallyouter surface of the seal ring.

It is preferred that the respective spigot projections are provided inthe region of their transversely projecting limits with respectivetapered or chamfered portions.

Typically, the spigot portion projects transversely from the web portionat least as far as the sealing lips project transversely from the webportion.

It is preferred that the web portion is provided with substantiallyparallel opposed radially extending surfaces which are advantageouslysubstantially parallel to the radial direction.

In one preferred embodiment of the invention, the spigot projections areprovided with respective further sealing means, such as respectiveperipheral sealing rims or the like.

In a further preferred embodiment, the sealing lips may be provided withannular plastically deformable rims at their transversely outermostprojecting limit. Typically the seal ring is principally or wholly ofmetallic material.

According to a second aspect of the invention, there is provided aconduit joint comprising a seal ring according to the first aspect ofthe invention interposed at an interface between a pair of conduit orvessel defining members, said members being provided at said interfacewith respective recessed portions complementarily shaped and dimensionedto receive respective portions of the spigot portion, and the sealingportion of the seal ring, respectively, wherein a first one of saidrecessed portions comprises an annular groove having substantiallyparallel radially spaced sidewalls, and a second one of said recessedportions comprises an annular surface sloping away from said interfacein an inwardly radial direction.

The annular surface sloping away from the interface in an inwardlyradial direction is, advantageously, frustoconical or part spherical.

In use, a spigot projection of the seal ring is received in the firstone of the recessed portions of a conduit or vessel defining member,with a respective sealing lip abutting the second one of said recessedportions. Corresponding first and second recessed portions of the otherconduit or vessel defining member are arranged to receive/abut thecorresponding other spigot projection and sealing lip of the seal ring.

Typically, the annular groove comprising first recess portion isprovided with substantially parallel radially spaced sidewalls which areconfigured substantially perpendicularly to the radial direction.Advantageously, the radially outermost sidewall of the annular groove issubstantially more extensive in a direction perpendicular to the radialdirection than the extent of the radially innermost sidewall of theannular groove in a direction perpendicular to the radial direction.

Advantageously, the radially innermost sidewall and radially outermostsidewall of the groove connect with respective substantiallyperpendicular facing surfaces of the respective conduit or vessel, atleast one of which surfaces is advantageously arranged to lie at aninterface between the pair of conduit or vessel defining surfaces. It ispreferred that the facing surfaces on each conduit or vessel definingmember are substantially parallel to one another, and advantageouslyspaced from one another in a direction transverse to the radialdirection.

Typically, the conduit-defining or vessel-defining members will beflanged members arranged to be bolted together with the seal ringinterposed therebetween to form a sealed joint. In one embodiment of theinvention, at least one of the member is a conduit-defining memberprovided with pressure tapping means extending from the exterior surfaceof the conduit-defining member to communicate with the respectiveinterface surface at a location, intermediate between the recessedportions, which is shaped to receive the spigot portion and sealingportion of the seal ring. In this embodiment it is generally necessaryto provide a pressure-balancing hole in the web portion.

The invention will now be further described in specific embodiments, byway of example only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a joint according to the secondaspect of the invention provided with a seal ring according to the firstaspect of the invention;

FIGS. 2 and 2A are a cross-sectional view of a part of the seal ring ofFIG. 1;

FIGS. 3 and 4 are sectional assembly views of part of the joint and sealring shown in FIGS. 1 and 2;

FIG. 5 is a sectional view of part of a modified joint and seal ringaccording to the invention;

FIGS. 6 and 7 are sectional assembly views of a part of a furthermodification of joint and seal ring according to the invention;

FIGS. 8 and 9 are sectional assembly views of parts of furthermodifications of joint and seal ring according to the invention; and

FIG. 10 is a cross-sectional view of a further modification of joint andseal ring according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, and initially to FIG. 1, a joint generallydesignated 1 comprises first and second flanged connecting members 2, 3bolted at an interface to define an axial fluid flow path or confinedspace, such as in a pressure vessel. An annular metallic seal ring 4(typically of low strength steel, such as mild steel or austeniticstainless steel) is provided at the interface interposed between theflanged members 2, 3 and serves to prevent fluid leaking out of thejoint at the interface.

The annular seal ring comprises a primary sealing portion 5 havingangled sealing lips 6, 7, a radially outwardly extending web portion 8,and a spigot portion 9 extending transversely to the web portion andconnected to the radially distal end thereof. As shown in FIG. 1, theprimary sealing portion 5 and spigot portion 9 are received inrespective complementary shaped recesses or grooves 10,11 extendingcircumferentially around the flanged connecting conduits at theirinterface.

The web portion 8 has opposed substantially parallel surfaces 8a, 8bwith the spigot portion 9 having opposed surfaces 9a, 9b extendingsubstantially perpendicularly thereto.

It is important that the thickness of the spigot portion 9 in the radialdirection (dimension w in FIG. 2A) is substantially greater than thethickness of the web portion 8 in the transverse direction (dimension tin FIG. 2A). This ensures that, when the seal ring 4 is in position in ajoint, there is substantially no deflection of the spigot portion 9 inthe radial direction relative to the web portion on tightening of thejoint; radial deflection of the seal ring is therefore generally limitedto radial stretch of the web portion and deflection of the seal lips ofthe sealing portion 5 thereby producing a more effective seal. Thisfeature also provides a stiff and rigid outer periphery for the sealring, which is particularly important where large seal rings (e.g.diameter dimensions of 0.3 metres or above) are required.

Furthermore, the provision of a thickened spigot portion 9 as described,ensures that shear stresses (which may result from connecting members 2,3 being non-coaxially aligned when the joint is formed) are taken up bythe spigot portion and not the web 8 or sealing portion 5 which wouldotherwise result in an inefficient seal being produced and/or damage.Typically a thickness ratio (w:t--see FIG. 2A) of at least 1.25:1 andpreferably greater than 1.5:1 produces enhanced seal ringcharacteristics. It is furthermore important that the sealing lips 6, 7project transversely from the web by a distance (dimension h in FIG. 2A)which is substantially greater than the thickness of the web 8 in thetransverse direction (i.e. dimension t in FIG. 2A). This ensures thatthe seal lips 6 may deflect radially to the required extent to producean efficient seal on tightening of the joint such that the respectivesealing point of the seal ring is displaced in the transverse directionfrom the web at an optimum distance.

It should also be noted that the spigot portion 9 extends transverselyto the web portion 8 to an extent as great as the primary sealingportion 5. If the seal ring 4 is dropped or knocked during transit orassembly, the impact shock and any resulting damage is therefore takenby the spigot portion 9, reducing the risk of damage to the sealing lips6, 7.

Referring to FIGS. 3 and 4, on assembly of the joint 1, each of theportions of the spigot portion projecting transversely to the webportion 8 engages with its respective annular recess 11 in the flangedmembers 2, 3 prior to the primary sealing lips 6, 7 initially contactingtheir respective sealing surfaces 12, 13 on the flanged members 2, 3.This is particularly important in preventing damage to the sealing lipswhere the flanged connecting members 2, 3 are slightly misaligned (i.e.not coaxial) and need to be forcibly aligned. As the flanged members 2,3 are aligned, the interface surfaces will "ride" over the ends of thespigot portion 9 and hence not damage the sealing lips 6, 7 on theprimary sealing portion 5.

Furthermore, as described above, once the joint is assembled, shearstresses exerted on the seal ring due to misalignment of the flangedmembers 2, 3 will be to a large extent taken up by the spigot portion 9and not the primary sealing portion 5. The construction thereforeensures that the primary sealing portion 5 takes up only the contactsealing stresses caused by tightening the flange connecting bolts (notshown). As described above, a further advantage of the spigot portion 9is that for large diameter seal rings (i.e. typically having a radius of0.3 metres or more), the rigidity of the seal ring is effectivelyincreased in the joint reducing the likelihood of unwanted flexion ofthe ring and enabling the general dimensions of the seal ring(particularly the web portion) to be kept to a minimum.

Prior to full tightening of the connecting bolts, the spigot portionwill be guilded in its respective annular recesses 10, 11 by means ofthe "lead in" chamfers 14 provided on the spigot portion 9. Under theaction of flange bolting, the flanged members 2, 3 are drawn togetheronto the seal ring causing seal lips 6, 7 to engage with respectivesealing surfaces of 12, 13 of the flanged members 2, 3.

As the seal lips 6, 7 are forced into the recessed seat formed by thesealing surfaces 12, 13 the seal ring lips 6, 7 bend radially inwards,and the whole seal ring including the spigot portion 9 is deflectedradially inwards. The radial deflection of the spigot portion can becontrolled (e.g. limited) by controlling (e.g. reducing) the clearancebetween radially innermost portion of the spigot portion 9 and theradially innermost wall of the annular receiving recess 11 such that ata predetermined inward radial deflection of the ring the radiallyinnermost portion of the spigot engages with the radially innermost wallof annular recess 11 thereby preventing further radial deflection of theseal ring as a whole. This forces additional radial deflection (bending)of the seal lips 6, 7 as the joint is tightened, which promotes highercontact forces and therefore higher contact stresses between the lips 6,7 and respective sealing surface 12, 13 for a ring of a givencross-section. Once the connection bolts are fully tightened and theseal ring is fully "engaged", a fluid seal preventing leakage of fluidfrom the interior conduit or vessel to the exterior of the joint isprovided. It should be noted that the pressure exerted on the seal ringby the fluid in the conduit or vessel has the effect of increasing thesealing contact stresses between lip 6 and sealing surface 12 and lip 7and sealing surface 13.

Referring to FIG. 5, a modification of the seal ring 5 and rangedconnection members 2, 3 is shown where the ranged member 3 is providedwith a pressure tapping 16 extending from the exterior of the joint (notshown) to the interior annular space around the web portion 8; there isfurther a pressure balancing hole 21 through web portion 8. Further seallips 17, 18 are provided on the spigot portion 9 which, when the seal isenergised, provide a seal on the radially innermost faces of annularrecesses 10, 11. Thus the region intermediate the spigot portion 9 andprimary sealing portion 5 is effectively sealed.

Leakage of fluid pressure applied to the pressure tapping 16 will givean indication of an inefficient seal having been set up in the joint,and thus provides an effective means of testing the efficiency of thesealed joint prior to pressurising the conduit with fluid.

Referring to FIG. 6 and 7, a modified seal is shown having seal lips 6,7 provided with a further sealing means in the form of crushablemetallic rims 19, 20. When the joint is assembled, the crushed rims 19,20 provide a further seal preventing ingress of potentially corrosivefluids to the primary sealing contact point of the lips 6, 7 withrespective surfaces of the ranged connection conduits 2, 3.

Referring to FIG. 8, in which like parts are denoted by like numerals,the seal ring has a circumferential groove 21 running around theoutermost face of spigot portion 9; such a groove can provide thefacility for the seal ring to be prised out after use and provide ameans of suspending the ring (via thin twine or similar) in the verticalplane between two flanges of a horizontal pipe run.

In a further variation shown in FIG. 9, the spigot has an outwardlytapering face 22, tapering outwardly from the web portion 8 (rather thansubstantially perpendicular thereto), and there is a corresponding taperon the facing surface 23 of the annular receiving recesses 10, 11.

Referring to FIG. 10, there is shown a modified seal ring 4 beinginterposed between a pair of misaligned flanged connecting members 2, 3.In this application, tightening of flange bolts 25 draws connectingmembers 2, 3 toward one another forming a seal between seal lips 6, 7and sealing surfaces 1, 13. The surface of sealing lips 6, 7 andsurfaces 12, 13 are part spherical to ensure a better seal whenenergised. The shear forces set up due to misalignment of the flangedconnecting members is taken up by both the spigot portion 9 and also thesealing portion 5. In applications where misaligned flanges are to beconnected, it is preferred that the sealing portion 5 is thicker in theradial direction than would otherwise be necessary. It should also benoted that, unlike in relation to the other embodiments described, inthe embodiment shown in FIG. 10, the flanged connection members 2, 3 donot abut one another once connected, thereby enabling the fulltightening force of bolts 25 to be taken up in the sealing portion 5.

I claim:
 1. An annular metallic seal ring substantially solid in cross-section and comprising a sealing portion, spigot portion and interconnecting web portion all formed integrally with one another, said sealing portion comprising a pair of annular seal lips facing the spigot portion and extending in a transverse direction to said web portion, which web portion extends radially outwardly from said pair of seal lips to said spigot portion, which spigot portion is provided with spigot projections projecting in mutually opposed directions transversely to the web portion, wherein the thickness of said spigot portion in the radial direction is at least 1.25 times the thickness of the web portion in the transverse direction, and each respective seal lip is arranged to project transversely from said web portion by a distance which is substantially greater than the thickness of said web portion in said transverse direction.
 2. A seal ting according to claim 1, wherein said pair of annular seal lips slope radially outwardly and toward one another to said web portion.
 3. A seal ting according to claim 1, wherein the thickness of the spigot portion in the radial direction is substantially greater than the thickness of the web in the transverse direction over substantially the whole transverse extent of the spigot portion.
 4. A seal ring according to claim 1, wherein each spigot projection is provided with a respective first transverse face portion facing a respective seal lip.
 5. A seal ting according to claim 4, wherein said respective first face portion is disposed substantially perpendicular to the radial direction.
 6. A seal ring according to claim 4, wherein each spigot projection is provided with a respective second transverse face portion spaced from the respective first transverse face position and facing in an opposed direction thereto.
 7. A seal ring according to claim 6, wherein the first and second transverse face portions provided on each spigot projection are substantially parallel to one another.
 8. A seal ring according to claim 6, wherein the second transverse faces comprise the radially outermost extent of the seal ring.
 9. A seal ring according to claim 1, wherein the respective spigot projections are provided in the region of their transversely projecting limits with respective tapered or chamfered portions.
 10. A seal ring according to claim 1, wherein the spigot projects transversely from the web portion at least as far as the sealing lips project transversely from the web portion.
 11. A conduit joint comprising a seal ring according to claim 10, interposed at an interface between a pair of conduit or vessel defining members, said members being provided at said interface with respective recessed portions complementarily shaped and dimensioned to receive respective portions of the spigot portion, and the sealing portion of the seal ring, respectively, wherein a first one of said recessed portions comprises an annular groove having substantially parallel radially spaced sidewalls, and a second one of said recessed portions comprises an annular surface sloping away from said interface in an inwardly radial direction and means to retain said members in sealing engagement with said seal ring.
 12. A seal ring according to claim 1, wherein the web portion is provided with substantially parallel opposed radially extending surfaces.
 13. A seal ring according to claim 1, wherein the seal lips are provided on respective radially outer portions of the sealing portion.
 14. A conduit joint comprising a seal ring according to claim 1, interposed at an interface between a pair of conduit or vessel defining members, said members being provided at said interface with respective recessed portions complementarily shaped and dimensioned to receive respective portions of the spigot portion, and the sealing portion of the seal ring, respectively, wherein a first one of said recessed portions comprises an annular groove having substantially parallel radially spaced sidewalls, and a second one of said recessed portions comprises an annular surface sloping away from said interface in an inwardly radial direction and means to retain said members in sealing engagement with said seal ring.
 15. A conduit joint according to claim 13, wherein the means to retain said members in sealing engagement with said seal ring includes flanges on said members arranged to be bolted together with the seal ring interposed therebetween to form a sealed joint.
 16. A conduit joint according to claim 14, wherein the annular groove comprises first recess portion is provided with substantially parallel radially spaced sidewalls which are configured substantially perpendicularly to the radial direction.
 17. A conduit joint according to claim 16, wherein the radially outermost sidewall of the annular groove is substantially more extensive in a direction perpendicular to the radial direction than the extent of the radially innermost sidewall of the annular groove in a direction perpendicular to the radial direction.
 18. An annular metallic seal ring substantially solid in cross-section and compnsing a sealing portion, spigot portion and interconnecting web portion formed integrally with one another, said sealing portion comprising a pair of annular seal lips facing the spigot portion and extending in a transverse direction to said web portion, which web portion extends radially outwardly from said pair of seal lips to said spigot portion, which spigot portion is provided with spigot projections projecting in mutually opposed directions transversely to the web portion, wherein the thickness of said spigot portion in the radial direction is at least 1.5 times the thickness of the web portion in the transverse direction, and each respective seal lip is arranged to project transversely from said web portion by a distance which is substantially greater than the thickness of said web portion in said transverse direction, said spigot projections projecting transversely from the web portion at least as far as the sealing lips project transversely from the web portion.
 19. A conduit joint comprising a seal ring according to claim 18, interposed at an interface between a pair of conduit or vessel defining members, said members being provided at said interface with respective recessed portions complementarily shaped and dimensioned to receive respective portions of the spigot portion, and the sealing portion of the seal ring, respectively, wherein a first one of said recessed portions comprises an annular groove having substantially parallel radially spaced sidewalls, and a second one of said recessed portions comprises an annular surface sloping away from said interface in an inwardly radial direction and means to retain said members in sealing engagement with said seal ring. 